Apple has released an important security update to High Sierra, available through the Updates tab in the Mac App Store>
Apple says "Install this update as soon as possible."
It's quick to download and does not require a restart.

Security Update 2017-001 is now being installed automatically, even if you manually installed previously. It changes the High Sierra build number to 17B1003. This apparently fixes the file sharing issue and bypasses having to manually install.

[Opinion] Comments in the article and in the comments section below repeat the trope that you should never install an update immediately. That ignores the extreme rarity of such a mistake. And it ignores the many security enhancements built into every update. And it ignores the continuous nature of updates, any one of which could theoretically fix an older bug but introduce a new one. There's no magic sweet spot in the update timeline. So I'll stick to my advice, which mirrors Apple's: keep your Mac updated for best security.

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